If it's a young chick, I'd give them Poultry Cell in their water every other day.
If it's an adult, then you can give it a human's Vitamin E pill directly in her mouth. Then give a little scrambled eggs for the selenium which helps it to absorb. 1/4 to 1/2, depending on size, of a human B-complex daily may help too. Both the E and the B I'd give daily for two weeks and evaluate if that's helping. If so, keep going.